The  mystical theology, as we said, has its deep source in the Tradition, which is to say in the mystery of the divine filiation which Jesus gives us to participate. 
He is the Son Of-Liked of the Father, the Only-One Born from Him, as we sing in the second antienne of the Holy Liturgy of St. John Chrysostome, each Sunday :
"Ô Son Unique and Verb (Word) of God, Thee the immortal, wich for our salvation has deigned take flesh of the Holy Mother of God and always Virgin Mary, Thee who without change became a man, Thee Christ God, Thee who have been crucified and by the death has wrestled death, Thee the One of the Holy Trinity, glorified with Father and the Holy Spirit, saves us"

The mystical theology consists in the deep knowledge of the Verb (Logos, Word of God) made flesh.This knowledge cannot be realized without a personal meeting with Him. It is here that we find the foundation of mystical theology, experience radical to which the theologien must continually return if he does not want to become a cymbal resounding which, certainly, can do a lot of noise but not good spiritual fruit.
The mystical experience begins with the personal meeting of Christ, the discovery of his Holy Face and the desire to enter in a real friendship with Him. This man-God, Jesus, begins to capture our eyes, to attract our attention, and our heart :  "He is". Here, it must insist on this "He is". That is the discovery, the "touch" of the humanity fantastically perfect of Christ and by this way the feeling of his divinity.
Jesus himself will tell us : "If you do not believe me that I Am, you will die in your sins ". The discovery (or rather the Revelation) of the " I Am " of Christ, in our hearts and our intelligence, evokes the contemplative dimension of our "Noûs" ( our contemplative intelligence in greek) and plunging us into a sense of awe and adoration.
Consequently, our relationship with Christ exchange in depth. He is not only  an exceptional man. He is not only a sublime man. He is my God and He is my brother in humanity as He became a man, a man like me. He is the Verb of God(Logos in greek) became flesh.
When the Philosopher Aristotle talks about the First Being, he shows that there are between the man and the God such a distance that friendship is impossible. The friendship calls for a certain equality. Certainly the God is not indifferent to men, and Aristotle is convinced that He has a small preference for men the most contemplatifs... There is a natural love of contemplative for this First Being, whose smaller knowledge is better than the knowledge the richest and most perfect of another reality. But this love cannot be achieved in a friendship.
The Christ transforms the relationship to God in a radical, prodigious! Now the Verb made flesh, without cease to be God becomes man and friendship divine is proposed to men. This friendship experienced of each of us with Jesus is itself the christian mystical experience. You understand that I am not speaking of mystical phenomena, charisms individuals... The mystical experience is fundamentally, radically, the mystery of friendship with divine Jesus lived fully under the breath of the Holy Spirit.